Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$19.44	10.356%	$21.4532	$21.45	$21.45	$21.50
Purchase #2	$210.85	7.218%	$226.0692	$226.07	$226.05	$226.10
Purchase #3	$223.67	12.125%	$250.79	$250.79	$250.80	$250.80
Purchase #4	$228.88	4.325%	$238.7791	$238.78	$238.80	$238.80
Purchase #5	$62.46	8.724%	$67.909	$67.91	$67.90	$67.90
Purchase #6	$143.50	10.769%	$158.9535	$158.95	$158.95	$159.00
Purchase #7	$73.90	13.429%	$83.824	$83.82	$83.80	$83.80
7 purchase totals =	$962.70		$1,047.7780	$1,047.77	$1,047.75	$1,047.90